Long-term mass balance of selected polythermal glaciers on Spitsbergen, Svalbard

Introduction

The change of the glacier surface elevation in time is given as the mass balance minus the glacier flux gradient, expressing mass conservation in a vertical column of ice (Paterson 1994): where h is the surface elevation at a given time t, q is the mass flux of ice along the flowline (δ x) and b is the net mass balance. The mass flux gradient describes the vertical flow velocity at a location (emergence velocity), which is upwards relative to the glacier surface in the ablation area and downwards in the accumulation area (Pater- son 1993). For two-dimensional flow the emergence velocity at a fixed location is (Paterson 1994, p. 258).